We are preparing precise and accurate models of the polysaccharide components (hyaluronate, the chondroitin sulfates, dermatan sulfate and keratan sulfate) of connective tissues. The molecular conformations, packing interactions and the binding of cations and water molecules are all being determined mainly by X-ray diffraction analyses of oriented and (sometimes) crystalline fibers. The dependence of the polyanion conformations and interactions on the type of cations present is being elucidated. BIBLIOGRAPHIC REFERENCES: Arnott, S. and W.T. Winter. 1976. Details of glycosaminoglycan conformations and intermolecular interactions. Fed. Proc. (in press). Winter, W.T., P.J.C. Smith and S. Arnott. 1976. The effect of calcium ions on hyaluronate structures. J. Mol. Biol. (in press).